Recently interest had increased in thermoplastic resin systems which contain desiccants or other adsorbents, especially where the resulting system is used to deliver an adsorption and/or desiccation function to an environment. This interest is especially apparent in the insulating glass industry where recent technological developments such as those described in U.S. Pat. Nos. 5,313,761 and 5,177,916 have proved to be reliant on the ability to deliver a flowable, adhesive desiccant formulation in the manufacture of insulating glass units.
Various formulations have been proposed to meet the needs of the insulating glass industry. Examples of formulations are disclosed in U.S. Pat. Nos. 5,510,416 and 5,632,122 as well as in PCT Published Application WO 96/08541.
While the existing formulations have significant commercial use, there is a constant desire to improve the formulations by minimizing the amount of resin component needed to deliver and maintain the necessary amount of desiccant in the desired location (e.g. adhered to a U-shaped window spacer).
In meeting the need for higher loading/more efficient formulations, it is generally desirable that the formulations are usable in existing equipment such that the implementation of the formulation would not require any additional expenditure for equipment by the user. Thus, it is highly desirable that the requirements for handling the formulation (i.e. heating, pumping, applying) do not become more severe. This presents a significant challenge in the context of flowable thermoplastic resin systems since the formulation viscosity typically increases sharply as a function of adsorbent loading just above the maximum practical loading for the specific formulation. Thus, simply increasing the amount of adsorbent even in a seemingly minor amount (or decreasing the amount of resin component) would result in a large increase in viscosity for the overall formulation at application temperature.
Additionally, it is desirable that the formulation not present any loss of performance in other aspects which may be important to the specific end use. Thus, where the formulation is to be used in an insulating glass unit such as described in the above mentioned patents, the formulation should resistant to slump and provide adequate adhesion to the window spacer.
The invention provides improved thermoplastic adsorbent compositions which enable reduction in the amount of resin needed to deliver a given amount of adsorbent without deterioration of viscosity/handling performance. The invention also provides improved thermoplastic adsorbent compositions which enable the delivery of a given amount of adsorbent more reliably and/or under less severe handling/application conditions.
In one aspect, the invention encompasses thermoplastic adsorbent compositions which contain (a) an adsorbent component and (b) a thermoplastic organic matrix component containing (i) wax, and (ii) thermoplastic polymer resin, wherein said wax has a weight average molecular weight of about 800-10000 and is compatible with the thermoplastic resin (i.e. not prone to phase separation or other adverse interaction when combined).
In another aspect, the invention encompasses thermoplastic adsorbent compositions which contain (a) an adsorbent component and (b) a thermoplastic organic matrix component wherein the composition contains at least 55 wt. % of adsorbent component and has an apparent viscosity of about 3xc3x97106 cP or less measured according to ASTM test D-3236-88 at 124xc2x0 C. and 0.125 secxe2x88x921 shear rate. The compositions are preferably adhesive and resistant to slump.
In another aspect, the invention encompasses insulating glass units containing thermoplastic adsorbent compositions which contain (a) an adsorbent component and (b) a thermoplastic organic matrix component containing (i) wax, and (ii) thermoplastic polymer resin, wherein the wax has a weight average molecular weight of about 800-10000 and is compatible with the thermoplastic resin (i.e. not prone to phase separation or other adverse interaction when combined). Preferably, the adsorbent component contains a desiccating adsorbent and the formulation desiccates a compartment partially defined by two or more panes of the insulating glass unit.
The compositions of the invention may also be used for other adsorption applications. These and other aspects of the invention are described in further detail below.